The invention relates to mine roof support assemblies and to guiding and aligning apparatus for the units of such an assembly.
When mine roof support units of the type having a floor sill and telescopic props for bracing against the roof of a mine excavation, are used in an excavation which dips, for example to follow a coal seam, steps have to be taken to prevent the units from slipping out of alignment and assuming an oblique position or tilting over when they are displaced in the direction of working face advance. For such purposes numerous guide and alignment devices are known, such as guide rail or guide rod systems with rigid guide rods or with hydraulic or mechanical telescopic guide rods. For example hydraulic telescopic guides may be interposed flexibly, and possibly on the universal joint principle, at a certain distance above the floor, between the props of adjacent units.
A guide system is also known in which the front and rear props of adjacent units are coupled via respective hydraulic telescopic guide rods, a diagonal hydraulic guide rod also connecting the rear prop of one unit with the front prop of the other unit. This guide rod system is constructionally expensive, as it requires, for all three telescopic guide rods, double-acting hydraulic piston-and-cylinder devices with appropriate hydraulic controls for controlling the retraction and extension of the devices during the shifting process. This guide rod system also necessitates using hydraulic piston-and-cylinder devices which have a long working stroke and which are, therefore, heavy, large and expensive; their length when retracted being equal to the distance between the props to which they are connected. This guide rod system involves the further drawback of seriously reducing the area available, between the props of the units.
Systems are also known in which spring biassed guide rods are provided between adjacent units. Apart from the comparatively high cost of such resilient guide rods, a guide rod system of this kind fails to ensure that the units will be adequately supported and guided by and aligned with one another, particularly in the event of any appreciable dip. This applies particularly when the guide rod system is to be used for guiding and aligning heavy units.
The main object of the invention is to provide a guiding and aligning apparatus for heavy mine roof support units which is simple, constructionally economical and of space-saving design.